1. Field of the Invention
The invention relates generally to electric gaseous discharge lamps and specifically to the construction and sealing of electrodes for such lamps within their glass tubes.
2. Description of the Prior Art
A gas-filled discharge lamp typically has an internal pressure of one atmosphere that will rise suddenly to approximately ten atmospheres when the gas is first ignited into a plasma by an electrical arc between electrodes.
U.S. Pat. No. 3,984,719, issued Oct. 5, 1976, to Egils M. Grasis, and one of the present inventors, Joseph R. Caruso, describes an internally sealed lamp that has its electrodes sealed within a glass tube envelope with elastomer O-rings. Such a system of envelope sealing has substantial positive economic benefits in the manufacture of large lamps.
Unfortunately, the pulsing that occurs each time a lamp ignites acts as an impact hammer against such O-ring seals and will ultimately force the seals and electrodes out of the glass envelope.
Prior art O-ring seal pump-down tubulations have been a challenge to make simple, neat electrical connections. The pinched-off end of the fill tube has been difficult to attach directly, and good electrical connections are needed to carry high peak currents and to reduce radio frequency emissions. Such electrical connections must also be simple to make and inexpensive to fabricate.
Prior art gaseous discharge lamps conventionally use metal bases, such as aluminum, for mounting. Such metal bases complicate the insulation system that is required to stand-off the very high voltages associated with such lamps, e.g., sixty thousand volts. A simplified insulation system is therefore needed to reduce overall lamp costs.